Study On The Algorithm Of Triangle Finite Element Mesh Generation

Automobile body cover panel parts play a very important role in automobile industry and its die design restrict the quality and renewal cycle of automobile. The finite element analysis of auto body cover panel stamping forming is important hinge from design to manufacture at present. Mesh generation is one of the key techniques of sheet forming simulation.There are many complex mechanics in sheet forming process including material, geometrical and contact nonlinear phenomenon. In order to get a correct design, we need to construct a reasonable numerical model of CAD. However, it depends on the quality of mesh after the numerical model constructed if we want to obtain a more close result to the actual situation. To ensure the calculating precision as well as reduce CPU time, to make a logical mesh is the base of forming simulation. About today's sheet metal forming CAE software, each has its own unique features. For example, Dynaform is good at the mesh handling and the results are precise but the calculating time is too long. Autoform has a advantage of calculating fast, but in the aspect of mesh processing few time for users to participate in the control and it has a poorer result than Dynaform's so it's suitable for the rough analysis of the CAE. However, these are foreign software and their introduction needs a very high price. So the most important thing for us is to develop our own software and only in this way can we break the passive situation of the long-term reliance on foreign technology. Therefore, it is inevitable and necessary for the development of our own domestic software.This paper took a nodes join method based on KMAS, a sheet metal forming CAE software. Basically on the ground of VC6.0, by programming of C++ language and ACIS functions, using the way of COMX, the approach of build parts based upon COM, to make KMAS mesh builder. In the beginning of analysis, to read CAD data model is needed and then to plot a reasonable mesh shape according to user's own definition of the mesh size and form. The data of mesh will be saved as NAS file format. After the simulation, if the calculation results can not meet user needs, we can amend the original CAD model or fix the mesh, including the size and form.The first chapter introduces the basic concept about cover panel die forming simulation,gives some examples of the CAE software and shows the situation of mesh generation nowadays. The second chapter introduces basal knowledge about mesh generation, such as methods about mesh generation, COMX build parts, function in ACIS forming software, Generic CAD surface storage format IGES file and mesh storage format NAS file. The third chapter introduces the method process of visible join in detail and gives an example of mesh generation using this method. The fourth chapter introduces the value of mesh quality and optimization. The last chapter introduces the generated mesh instances using the software on which the programs were based.This paper, aiming at automobile cover panel numerical simulation analysis, makes a systemic and in-depth study of the finite element mesh generation technology in the stamping forming, proposes a triangle algorithm of mesh generation lined with the Finite Element Analysis and gives the mesh generation programs. Its basic principle is that the geometry internal layout and boundary discretion and then using a given node in accordance with the rules of visible joining to link a triangular unit. The biggest feature of this method is that the parts forming the units are always maintaining convex polygon, and not restricted by internal holes so it has a high speed of mesh generation. However, the quality of the mesh is affected so much by grid layout of the initial phase, so it needs the smoothing treatment later. Design an optimization algorithm which is the combination of geometric optimization and topology optimization. Topology Optimization by adjusting the mesh topology has been generated to the grid optimization to ensure that the followed-up grids'shape and size. The geometric optimization adjusts all of the inner mesh by regulating the location of inner nodes after mesh generating. The combination of the two methods greatly improves the quality of mesh, provides conditions for the solution followed and makes the results be closer to the practical one. After the mesh generator, a lot of parts are tested and the results show that the algorithm generates mesh fast and uniformly.This thesis's main topics of research are shown as follows:1. Proposes a visible nodes joining algorithm of mesh generation and makes it come true.2. Discusses the rules of mesh subdivision and polymerization and achieves dynamic adaption for itself of FEM.3. Studies the format of IGES file, NAS file and ACIS forming technology.4. Gives a standard of mesh quality and studies and works out the mesh optimization algorithm.